This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. xc2xa7 119 from an application entitled A Colour Selecting Apparatus for Cathode Ray Tube earlier filed in the Korean Industrial Property Office on Jan. 31, 2000, and there duly assigned Ser. No. 2000-4680 by that Office.
1. Field of the Invention
The present invention relates to a color selecting apparatus for a cathode-ray tube, and more particularly, to a color selecting apparatus having a tensed mask, which includes a pair of vibration attenuating members for preventing the so-called howling phenomenon due to vibrations of the mask.
2. Description of the Background Art
In general, a cathode-ray tube is used for displaying an image by emitting light on a phosphor screen with electron beams generated from an electron gun assembly. The cathode-ray tube includes a shadow mask as a color selecting electrode for separating three electron beams to corresponding red (R), green (G) and blue (B) phosphor layers on the screen.
The shadow mask is made by forming a plurality of beam-passing apertures on a thin aluminium-killed (AK) steel or an INVAR steel by the well-known photolithography process. Killed steel is deoxidized by the addition of deoxidizing elements such as aluminum in the ladle prior to ingot casting to form aluminum-killed steel. INVAR steel is a trademark for a steel alloy containing approximately 36% to 50% nickel (Ni) and the rest iron (Fe). INVAR steel has a low coefficient of thermal expansion.
The shadow mask is apt to be depressed due to an external impact since the shadow mask is formed in an extremely thin thickness over a relatively wide area with beam-passing apertures, decreasing the strength thereof. Further, the so-called doming phenomenon, which refers to the expansion toward the phosphor screen due to the continuous radiation of electron beams, may occur in the shadow mask.
If the shadow mask is deformed or the doming phenomenon occurs as described above, the positions of the beam-passing apertures are altered so that precise color separation of the electron beams is disturbed, and thereby the degree of purity of the images is degraded.
Therefore, in order to overcome the above defects and to meet the tendencies toward the super flat screen, a tensed mask that is supported in a frame with tension force has been suggested.
A tensed mask includes a hole part formed with a plurality of beam-passing apertures, and a non-hole part positioned to surround four edges of the hole part. The tensed mask is spot-welded on the frame and supported by the frame with tension applied on the mask. The tensed mask constructed as above is especially appropriate to a flat screen and has advantages in that thermal expansion is restrained by the tension force and accordingly the doming phenomenon is effectively prevented.
However, the tensed mask is sensitive to vibration and has disadvantages in that vibration is apt to be generated due to not only external vibration energy, but also an external energy applied by the complex influence exerted by the spot-welding state with the frame, the thickness of the mask itself, and the alignment of the beam-passing apertures 1a, etc. Such vibrations continue for a long period, for example about 10 minutes, due to the influence of sound waves coming out from the speakers.
The phenomenon that degrades the quality of the images due to the long-term vibration of the tensed mask caused by the external energy is the so-called howling phenomenon. The howling phenomenon is generated at both right and left sides of the tensed mask, that are near the speakers, and generally disposed at both sides of the screen, producing sounds.
The howling phenomenon is usually generated in one part of a tensed mask positioned approximately 5 millimeters within both the right and left edges of the hole part, degrading the purity of colors at both right and left ends of the screen.
Exemplars of the art are U.S. Pat. No. 5,167,557 issued to Teramoto et al. discloses Method for Manufacturing a Shadow Mask, U.S. Pat. No. 5,484,074 issued to Deibler et al. discloses Method for Manufacturing a Shadow Mask, U.S. Pat. No. 5,451,833 issued to Tong discloses Shadow Mask Damping for Color CRT, U.S. Pat. No. 6,133,682 issued to Murai et al. discloses Color Cathode Ray Tube Having Shadow Mask with Prescribed Bridge Widths, U.S. Pat. No. 6,104,132 issued to Nose et al. discloses Color Cathode Ray Tube, U.S. Pat. No. 6,046,535 issued to Jung et al. discloses Shadow Mask Frame Assembly for a Cathode Ray Tube, U.S. Pat. No. 6,025,676 issued to Ohama et al discloses Cathode Ray Tube Having Improved Curvature Characteristics and Method of Fabrication Thereof, U.S. Pat. No. 5,917,273 issued to Watanabe et al. discloses Color Cathode-Ray Tube Including a Shadow Mask having Holes Arranged with a Monotonically Non-Decreasing Arrangement Pitch, U.S. Pat. No. 5,682,021 issued to Jeon et al. discloses Howling Phenomena Removing Apparatus for Video Display Appliances, and U.S. Pat. No. 5,289,080 issued to Park discloses Mask Frame Damper for Color Cathode Ray Tubes.
It is therefore an object of the present invention to provide a color selecting apparatus for a cathode-ray tube that is capable of preventing the so-called howling phenomenon by attenuating vibrations applied to a tensed mask, especially vibrations generated by speakers.
It is another object to have a strong frame structure surrounding a mask in an electron beam apparatus.
It is yet another object to have an electron beam apparatus that reduces the howling phenomenon.
It is still yet another object to have a cathode-ray tube that can avoid the howling phenomenon and still be easily manufactured without heavily increasing manufacturing costs.
In order to achieve the above objects, the color selecting apparatus includes a frame, and a mask supported in the frame with tension along a minor axis, where the mask has a rectangular hole part formed with a plurality of electron beam-passing apertures, a non-hole part positioned surrounding the hole part, and a pair of vibration attenuating members attached at both ends of a surface of the non-hole part, facing each other along a major axis, for attenuating vibration waves that are transmitted on the major axis.
The vibration attenuating members are made of a metal having a greater mass than the non-hole part, and are attached by spot-welding so that they are away from the non-hole part by a predetermined gap in every portion except the welding points. Accordingly, the vibration attenuating members serve as dampers to attenuate vibrations which are transmitted in the major direction, particularly vibrations generated by the speakers, that are apt to cause the howling phenomenon.